An air-conditioning apparatus in the related art is configured so as to prevent liquid compression of liquid refrigerant that has stagnated in the compressor while the compressor is stopped by outputting a signal when the amount of liquid refrigerant stagnating in the compressor increases to a predetermined value or larger and with a control unit distributing a weak high-frequency open-phase current to a motor coil to warm up the motor coil upon input of the signal. Liquid compression caused by starting the operation while the refrigerant is in a dormant state, that is, in a state in which the stagnating liquid refrigerant in the compressor is at a low temperature, is prevented and thus damage of the compressor is prevented (for example, see PTL 1).
There is also a configuration in which sufficient preheating is achieved with minimum electrical current consumption by periodically inverting the direction of current flowing through a stator coil of a motor by means of controlling an ON/OFF cycle of a switching element to generate heat not only by conventional resistance loss but also by hysteresis loss and, furthermore, by reducing the number of switching operations per unit time, thereby improving power efficiency (for example, see PTL 2).